The present invention departs from problems which are encountered in manufacturing filled containers and as will be exemplified referring to FIGS. 1 to 10.
In FIG. 1 there is shown a container 1 which comprises a first part 1a and a second part 1b. The first part 1a is conceived as a receptacle and is filled with a product P as e.g. with a foodstuff, e.g. yoghurt. The second part 1b is conceived as a covering foil or lid, which is sealingly bonded to the part 1a along a bond area 3.
In top view the container 1 may have a great variety of shapes, some examples being shown in FIGS. 2 to 4. According to FIG. 2 the container 1 as of FIG. 1 is cylindrical or cone shaped and the bond area 3 is circular.
According to FIGS. 3 and 4 the container 1 has a shape departing from circular, conceived with a shape resulting from fantasy of the container manufacturer. There the shape of the bond area 3 largely departs from circular and may in fact have practically any looped shape.
According to FIG. 5 the container 1 with an outer shape e.g. as shown in FIG. 1 has a part 1a which is filled e.g. with two filling products Pa and Pb in two respective compartments which are separated by a separating wall 5, e.g. being an integral part of the container part 1a. Accordingly the bonding area 3 by which the second part 1b is sealingly bonded to the part 1a of the container 1 has, as shown in top view in FIG. 6, not only a looping area but additionally an area which crosses that loop. FIGS. 7 and 8 show, departing from the container shapes as exemplified in the FIGS. 3 and 4, such containers and the resulting bonding area 3 when e.g. their part 1a according to FIG. 1 is subdivided by additional walls into two or more than two distinct compartments. From FIGS. 1 to 8 it results that the bonding area 3 may have practically any shape.
Further, and as shown in FIG. 9, the second part of a container 1 needs not be a foil or lid part, but may be a second receptacle part. According to FIG. 9 the container 1 comprises part 1a formed as a receptacle and part 1c formed as a receptacle too. These two parts are bonded along bond area 3. Thereby, the container 1 may contain one single product, so that no separation is provided within container 1. If the container 1 contains e.g. two products Pa and Pb, which shall not be mixed within the container 1, one or even two separating foils 7 are provided and the bond area 3 preferably links the parts 1a, 1c as well as the foils 7. Additionally, the technique as shown in FIG. 9 may be combined with subdivision of the parts 1a and/or 1c by walls as shown in FIGS. 5 to 8.
All the bond areas 3 as exemplified in the FIGS. 1 to 9 have in cross-section as shown in FIG. 6 at Xxe2x80x94X the structure as shown in FIG. 10. Two or more than two, according to FIG. 10 e.g. three, materials A, B, possibly C . . . are as schematically shown bonded together at the bond area 3, which is in said cross-sectional view substantially flat. Thus, the bonding area 3 is in fact band-shaped. Bonding may be done by any known technique for the addressed purpose, as by gluing, welding etc. More specifically bonding may be performed in a preferred form by ultrasonic sealing, high frequency sealing or heat contact sealing. In this context the addressed xe2x80x9cbondingxe2x80x9d is often referred to e.g. in literature as xe2x80x9csealingxe2x80x9d. Further, the material as of A, B, C . . . of FIG. 10 may be, considered in subsequent pairs, equal or different, thereby being e.g. plastic material, metal material as of aluminum for foils, coated metal material etc.
We define generically surfaces along which two material phases contact each others, even if the contacting materials are equal and just lay one upon the other, as material interfaces. Thus, according to FIG. 10 a first material interface is formed between material C and ambient air, a second between material B and material C and a third between material A and B, a fourth again between ambient air and material A.
By the addressed bond areas 3 one or more than one filling product of the container 1 are encapsulated. If the bond area 3 does not provide for a high quality joint and according to the degree of bonding failure, air may be entrapped or filling product may pour out of the container 1 more or less rapidly or become entrapped too within the bond, and may start to deteriorate over time. Also other contaminants may be entrapped in the bond area. Depending on the kind of product contained in such containers, e.g. medical products, food products, a locally inaccurate or disturbed bondage along the bond areas 3 may cause tremendous problems. Thereby, an inaccurate bond along the bond area needs not necessarily be detectable by a leak testing technique, because as addressed above e.g. a material entrapped within the bond might not deteriorate the container""s unleakyness, but may on shorter or longer terms cause tremendous deterioration of the filling product, up to making such container leaky only after some time of storage.
It is therefore an object of the present invention to provide a method for manufacturing containers of the kind as described with the help of the FIGS. 1 to 10, whereat an essential step of manufacturing is testing the bond area on its quality, i.e. testing xe2x80x9cseal integrityxe2x80x9d, so as to produce such container with high quality bond, i.e. xe2x80x9csealxe2x80x9d area.
From the article xe2x80x9cHigh contrast ultrasound images of defects in food package sealsxe2x80x9d, Catherine H. Frazier et al., IEEE Transactions on ultrasonics, ferroelectrics, and frequency control, Vol. 47, No. 3, May 2000, investigation of bond areas by ultrasonic response evaluation is known. It is an object of the present invention to improve such testing approach with respect to accuracy and reproducibility.
This is achieved under a first aspect of the present invention by the method of manufacturing filled containers which comprises the steps of providing at least a first and a second part of the container, providing a product within at least one of the first and the second part, assembling the first and the second parts by bonding a portion of the first part to a portion of the second part, thereby generating a bond area, scanning along the bond area with a transmitted beam of a pulse train of ultrasonic energy, sensing a reflected pulse train of ultrasonic energy from the bond area, determining time derivative of at least one of time lag and of amplitude of the sensed pulse train, generating a signal indicative of the quality of the bond along the bond area by comparing at least one of the time derivatives with a predetermined threshold value and separating containers if the indicative signal indicates a bond along said bond area which is inaccurate.
Thereby, in a most preferred embodiment the beam of pulse train is led towards and onto the bond area and the reflected pulse train is led from the bond area at least to a predominant part exclusively through liquid. Thereby, it is achieved that at least a predominant part of ultrasonic energy from a respective generator to the bond area and back to an ultrasonic energy sensor is exclusively led through the liquid.
In a further most preferred embodiment the beam of pulse train is directed in a direction towards and onto the bond area, which is different from perpendicularly thereto considered in a plane which is defined by a perpendicular line on the bond area and scanning direction of the beam along the bond area.
In further preferred embodiments the bond area to be investigated forms a loop, thereby preferably an at least substantially planar loop. Thereby, further preferably, the loop is at least substantially circular.
In a further preferred embodiment the bond area defines for at least three materials stacked one upon the other, whereby respectively two of the materials concomitantly form a material interface. Then sensing comprises sensing a reflected pulse train of ultrasonic energy from at least one of the material interfaces. In a bond area where two rigid materials, as e.g. a metal foil is bonded to a plastic material, three materials appear stacked one upon the other, namely the plastic material upon which resides the foil material and finally ambient air or another ambient material as a liquid, so that three material interfaces are formed. This to clarify definition and counting of material interfaces.
In a further preferred embodiment the scanned path of the pulse train of ultrasonic energy along the bond area is monitored or measured, and the location along the bond area at which the indicative signal is generated, which indicates an inaccurate bond, is identified. This allows for information about failure at a bonding station as e.g. about failure of a bonding tool.
So as to facilitate evaluation of the sensed impulse train it is further preferred to select the duty cycle and the pulse repetition frequency of the pulse train so that the pulse train as transmitted does not overlap a reflected and sensed pulse train at the sensing location. Further, in a most preferred embodiment the beam is generated substantially coaxially to an axis of highest sensitivity of ultrasonic energy sensing. An ultrasonic energy sensor defines for a reception lobe of ultrasonic energy sensing amplification. Such reception lobe defines for the addressed axis of highest sensitivity. The transmitted beam is thereby transmitted coaxially to this axis.
In a further preferred mode of operating the inventive method the direction with which the beam is directed towards and onto the bond area defines for an angle xcex1 with a perpendicular line or normal on the bond area in a plane defined by said normal and direction of scanning which angle fulfills the following conditions:
0xc2x0 less than xcex1xe2x89xa630xc2x0,
preferably
5xc2x0xe2x89xa6xcex1xe2x89xa620xc2x0,
and thereby most preferred the relation
10xc2x0xe2x89xa6xcex1xe2x89xa618xc2x0.
A first preferred embodiment of realizing conductance of the substantial part of ultrasonic energy through a liquid is realized in that at least the bond area of the container, an output of an electrical to mechanical converter for generating the beam as well as the input of a mechanical to electrical converter for sensing the reflected pulse train are immersed into a liquid. In another preferred embodiment of realizing this ultrasonic energy conductance in a liquid is realized by establishing locally a bridge of the liquid from the said output of the electrical to mechanical converter for generating the ultrasonic beam to the bond area and then to an input of the mechanical to electrical converter for sensing the reflected ultrasonic energy. Thereby, in a further preferred embodiment the bridge of the liquid is established by applying the liquid locally on the bond area and suctioning the liquid from the bond area just after such area having been subjected to scanning.
In a most preferred embodiment water is selected as liquid. In a further preferred embodiment and with an eye on scanning technique such scanning is realized by moving the beam along the bonding area of the container which former is kept stationary. In another preferred embodiment the beam is moved whereas the container is kept stationary for the addressed scanning. In still another preferred embodiment scanning is performed by moving the container as well as moving the beam.
Still in a further preferred embodiment the trajectory path for scanning is predetermined, so that scanning movement control may be realized on the basis of such predetermined trajectory. In another preferred embodiment, whereat accuracy and repeatability of the shape of the bond area may not be predetermined accurately enough, the course of the bond area is traced as by a picturing head and the relative movement of container and beam is controlled by the tracing result.
So as to establish stable and reproducible position of the containers to be investigated, especially if no use is made of bond area tracing techniques, in a preferred embodiment the container is positioned by suctioning action, whereby the container is suctioned-drawn into a predetermined position.
Under a second aspect of the present invention to fulfill the object as mentioned above at least a first and a second part of the container are provided, at least one of these parts is filled with a product, the two parts are assembled by bonding a portion of the first part to a portion of the second part, whereby a bond area is generated. Then the bond area is scanned with a transmitted beam of ultrasonic energy and reflected ultrasonic energy from the bond area is sensed. From the sensed ultrasonic energy there is generated a signal which is indicative of the quality of the bond along the bond area. Thereby, under this aspect the ultrasonic energy from a mechanical output of an electric to mechanical converter to generate the transmitted beam onto the bond area and said reflected ultrasonic energy from the bond area towards and onto a mechanical input of a mechanical to electrical converter for sensing the reflected ultrasonic energy is performed in a liquid. This technique under the second aspect of the present invention may preferably be combined with one or more than one of the above mentioned aspects.
Under a third aspect of the invention still to fulfill the above mentioned object again there is provided at least a first and a second part of a container to be investigated, a product is provided within at least one of these two parts, the first and second parts are assembled by bonding a portion of the first part to a portion of the second part, thereby generating a bond area. The bond area is scanned with a transmitted beam of ultrasonic energy, and reflected ultrasonic energy from the bond area is sensed. There is generated from the sensed ultrasonic energy a signal which is indicative of quality of the bond along the bond area. Thereby, further, the direction of the beam of ultrasonic energy towards and onto the bond area is selected to be different from perpendicularly on said bond area and considered in a plane defined by a perpendicular line or normal on the bond area and the scanning direction. Again and also under this third aspect of the invention the above mentioned different preferred embodiments are combined by two or more than two with the invention under this aspect.